Stability Relations of Bredigite (5CaO· MgO· 3SiO<sub>2</sub>)

Lin, H. C.; Foster, W.

doi:10.1111/j.1151-2916.1975.tb18991.x

Cited by 9 publications

(3 citation statements)

References 5 publications

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“…Thanks to enormous effort along all these years, it has become generally clear that the Bre from Scawt Hill is compositionally identical to "Phase T" experimentally observed by Gutt [7,8], with mutual substitution of Ca and Mg to some small extents [17,20] but without any significant Ba in the structure [11,14,16,19]. It has also become clear that Bre is stable up to~1372 • C at ambient P [8][9][10]12,17]. Recently Xiong [20] experimentally demonstrated that Bre is stable at~1.2 GPa.…”

Section: Introductionmentioning

confidence: 75%

“…The word "bredigite", abbreviated as Bre hereafter, was first used by Tilley and Vincent [5] to describe a mineral coexisting with spurrite, larnite, and gehlenite in the contact zone of Chalk and Tertiary dolerite at Scawt Hill, Northern Ireland. It caused substantial confusion in terms of chemical composition, phase stability, and crystallographic structure [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Thanks to enormous effort along all these years, it has become generally clear that the Bre from Scawt Hill is compositionally identical to "Phase T" experimentally observed by Gutt [7,8], with mutual substitution of Ca and Mg to some small extents [17,20] but without any significant Ba in the structure [11,14,16,19].…”

Section: Introductionmentioning

confidence: 99%

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Crystal Structure and Some Thermodynamic Properties of Ca7MgSi4O16-Bredigite

Bao

Zhang

et al. 2020

Crystals

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Bredigite with the composition Ca7MgSi4O16 (Ca7MgSi4O16-Bre) has been synthesized by a solid-state reaction method at 1.2 GPa and 1373 K for 7 days, and its structure has been determined by single-crystal X-ray diffraction data. Following a relevant genealogy analysis in the literature, we have refined the structure into two space groups, Pnnm and Pnn2, and found that Ca7MgSi4O16-Bre belongs to the space group Pnnm, which can be essentially derived from the space group Pnn2 via an atomic coordinate transformation (with an average deviation of 0.039 Å only). Furthermore, some thermodynamic properties of the Ca7MgSi4O16-Bre have been obtained in this study. Using first-principles simulations based on density functional theory, the isothermal bulk modulus has been determined as 90.6(4) GPa with a pressure derivative of 5.7(1). Using density functional perturbation technique, the phonon dispersions and vibrational density of the states (VDoS) have been calculated. The VDoS has been combined with a quasi-harmonic approximation to compute the isobaric heat capacity (Cp) and standard vibrational entropy (S2980), yielding Cp = 8.22(2) × 102 − 3.76(6) × 103T−0.5 − 1.384(4) × 107T−2 + 1.61(8) × 109T−3 J mol−1 K−1 for the T range of 298-1000 K and S2980 = 534.1 (22) J mol−1 K−1.

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Section: Introductionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Crystal Structure and Some Thermodynamic Properties of Ca7MgSi4O16-Bredigite

Bao

Zhang

et al. 2020

Crystals

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“…The above reactions followed by the fact that calcium oxide has greater affinity to silica, and, therefore, it form more stable suitable silicate than magnesium oxide [10,11]:…”

Section: Introductionmentioning

confidence: 99%

Validation of FeSiMg Alloy Production Model for the Experimental Process

Ghali

Eissa

El-Faramawy

2012

Journal of Metallurgy

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This paper investigates the effect of limestone, bauxite, fluorspar, and quartzite additions on the magnesium recovery in FeSiMg production from dolomite. Also, it illustrates the validation of the previous designed model. According to the model, magnesium content in the product alloy is calculated by the equation [Mg]=(MgO0)[Si0][eKt[(MgO0)-[Si0]]-1]/((MgO0)[eKt[(MgO0)-[Si0]]]-[Si0]), where [Mg] is the concentration of magnesium metal in ferrosilicon magnesium alloy in mol/L, [Si0] and (MgO0) are the initial concentrations of silicon and magnesium oxide in charge in mol/L, t is the time in seconds, and K is the reaction rate constant (3.26588×10-7 LSec−1 mol−1). The results of the production process are compared with the model results. The deviation between the actual and predicted magnesium content decreases as fluorspar, limestone, and quartzite increase up to 12.8wt.%, 8wt.%, and 8wt.%, respectively, with increase in the amount of the additives, the magnesium content in the produced alloy becomes far from the predicted values. It was found also that the addition of bauxite increases the gap between the actual and predicted values of magnesium content. It was found that the deviation of the actual magnesium content from the predicted depends mainly on the viscosity of the slag.

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